Question

Two similar prisms have heights 4 cm and 10 cm. What is the ratio of their surface areas?

A) 2:5
B) 4:25
C) 4:10
D) 8:125

Answer 1

4:25 is the correct answer

Answer 2

H 1 : H 2 = 4 : 10
H 1 = 2/5 H 2
and also for the base: L 1 = 2/5 L 2 and W 1 = 2/5 L 2
A 1 = 2 L 1 x W 1 + 2 L 1 x H 1 + 2 W 1 x H 1
A 2 = 2 L 2 x W 2 + 2 L 2 x H 2 + 2 W 2 x H 2
A 1 / A 2 = 4/25 *( 2 L 2 x W 2 + 2 L 2 x H 2 + 2 W 2 H 2 ) /
/ ( 2 L 2 x W 2 + 2 L 2 x H 2 + 2 W 2 x H 2 ) =
= 4/5
A 1 : A 2 = 4 : 25
Answer: B ) 4 : 25